**4. Effects of digestate on soil properties**

Digestate is a very complex material therefore its using has effect on the wide range of physical, chemical and biological properties of the soil, depending on the soil types (Makádi et al., 2008). The recycled organic wastes are suitable for contribution to maintain the soil nutrient levels and soil fertility (Tambone et al., 2007). Among the organic amendments the ratio of liquid digestate in the agriculture is known to be around of 10%. It can be applied as

Digestate: A New Nutrient Source – Review 301

Generally, the digestate application does not cause any significant changes in the total-N and available P content, while the available K content was increased by the application of biogas residue (Olsen et al., 2008). Similar results have found Vágó et al. (2009), who reported the significant increase of 0.01 M dm-3 CaCl2 extractable P content even after 5 L m-2 digestate treatment, while the K content of soil was significantly increased by

After the application of the digestate in 5 and 10 L ha-1 dosages, the Cd, Co, Cu, Ni and Sr content of soil solutions did not change. The Zn content decreased significantly, while the

The increasing soluble P content of digestate treated soil decreased the available Zn content in the soil solution by building slightly soluble zinc-phosphate residue (Vágó et al., 2009).

Soil OM decreases in crop soils in Europe and in other continents therefore using

Digestate contains high amount of volatile fatty acid (C2-C5) which could be decomposed within few days in the soil (Kirchmann & Lundwall, 1993). The greatest rate of decomposition were observed in the first day after the treatment (Marcato et al., 2009) but the mineralization rate were high during the first 30 days (Plaza et al., 2007). Moreover, the C-mineralization values from the soil incubation assay showed that the results of raw slurry were similar to the effect of compost being in the start of composting process while the digested slurry had similar C-mineralization rate in the soil samples than that of the

Soil microbial community has an important role in the fertility of soil and its alteration after intervention to the soil (e.g. manuring, soil improving, soil pollution) could be indicate more

sensitive these changes than changes in the soil physical and chemical properties.

amount of manganese (Mn) increased by almost 40% (Vágó et al., 2009) (Table 5).

(extraction with 0.01 M dm-3 CaCO3). (*Data from Vágó et al., 2009*).

amendments for increasing the soil OM content has a particular interest.

**4.5 Effect of digestate on the microbiological activity of soil** 

**4.4 Effect of digestate on soil organic matter content** 

matured compost (Marcato et al., 2009).

Element Control 5 L ha-1 digestate 10 L ha-1 digestate Cd 0.063 0.067 0.055 Co 0.064 0.071 0.057 Cu 0.089 0.112 0.118 Mn 25.5 35.1 35.5 Ni 0.50 0.52 0.35 Sr 8.56 8.60 8.62 Zn 1.40 0.98 0.062 Table 5. Microelement content of soil samples (mg kg-1) treated with liquid digestate

10 L m-2 digestate dose only.

**4.3 Effect of digestate on soil microelement** 

a fertilizer, but it could be appropriate as a soil quality amendment (Schleiss and Barth, 2008). Comparing to the other organic materials, the amendment properties rank sequentially as compost ~ digestate > digested sludge >> ingestate, on the bases of OM degradability (Tambone et al., 2010).
